Two-cycle internal-combustion engine of the non-diesel type operating on gas fuels



Feb. 18, 1930. w, HUBBELL 1,747,171

TWO-CYCLE INTERNAL COMBUSTION ENGINE OF THE NON-DIESEL TYPE OPERATING 0N GAS FUELS Filed Oct. 19, 1927 Patented Feb. 18, 1930 UNITED STATES PATENT. OFFICE ALFRED W. HUBBELL, OF BARTLESVILLE, OKLAHOMA, ASSIGNOR TO CLARK BROS. 00., OF OLEAN, NEW YORK, A CORPORATION OF NEW YORK TWO-CYCLE INTERNAL-COMBUSTION ENGINE OF THE NON-DIESEL TYPE OPERATING ON GAS FUELS Application filed October 19, 1927. Serial No. 227,121.

It is to be understood that where I refer to gas fuels herein, I refer to fuels that are initially gaseous in form, as distinguished from carbureted mixtures of liquid fuels. My invention is concerned only with two-cycle engines operating on gas fuels and of the kind in which the fuel is admitted to the engine cylinder early in the compression stroke and is ignited by a spark or. the like,

In the ordinary two-cycle engine of the kind here concerned, it is well-known that a considerable fraction of the fuel is lost by a part of the combustible mixture following or accompanying the last of the burned gases through the exhaust port in the scavenging operation. While two-cycle engines are preferred to four-cycle because of the comparative simplicity of the former, in this respect two-cycle engines are less efficient than four-cycle engines in which these losses of fuel do not occur.

A number of years ago it was proposed to eliminate this loss of fuel in two-cycle en gines by using air alone to blow out the burned exhaust gases, delaying the admission of the fuel until after the closing of the exhaust ports, and many different forms of engines have since been devised operating on this principle, both for gas fuels and for carburetted mixtures of liquid fuels. So far as I am aware however, none of these engines have been found adapted for commercial uses. Certain of these prior designs have features more or less peculiar to the particular designs, .which undoubtedly render them undesirable. As a whole however, I believe that all these prior designs add so much additional structure as to destroy the advantage of comparative simplicity which the twocycle engine otherwise possesses. In particular, I think that the fuel pump or pumping mechanism which I believe is used in all these prior designs for compressing the fuel (or a mixture of fuel and air) renders these designs non-commercial. In some instances this pump is a step on the engine piston; in others, it is a separate pump attached to and driven by the engine. Whatever its form may be, I believe that the addition of this pumping mechanism to the otherwise simple two-cycle engine adds undulyto the initial cost and the operating and maintenance troubles and expense. This pump alone therefore, in my estimation, is sufficient to explain why engines operating on this obviously-desirable delayed-fuel-admission principle have not come into use. Regardless of the correctness of my beliefs however, the factremains that non-Diesel type two cycle englnes operating on the delayed-fueladmission principle have not come into use, or at least extensive use, in any form or for any purpose.

In certain limited situations however, namely, Where gas fuel is already available under pressure,for example, and especially, in oil fields where natural gas is available, I have found how the delayed-fuel-admission principle can be applied to non-Diesel twocycle engines in a practical manner. Compared to the ordinary form of two-cycle engines previously used in these situations, the saving in fuel gas has amounted to more than twenty-five per cent in some instances, and the efliciency of the two-cycle engine has been raised to substantially the efliciency of the four-cycle engine without greatly increasing-its complexity. To this end, I take the gas fuel from the available source of gas under pressure, thus rendering a special pump for the fuel unnecessary. With this feature I combine'certain others. According to my invention: The exhausted burned gases are blown out by air without the admixture of fuel, although there is no objection to the addition of some fuel to the scavenging air except for the loss of fuel such practice entails. The combustion air maybe a remnant of the scavenging air. As assumed by the delayed-fuel-admission principle, the gas fuel, under some super-atmospheric pressure, is put in later; there need be no admixture of air to the gas, and preferably there is none, although there is no insuperable objection to a mixture of air with the fuel gas if the mixture under pressure can be obtained without the complications I seek to avoid. This gas I take from the available source of gas under pressure as before mentioned; the source may be a gas main or gas holder.

Where necessary (as will usually be the case) as Where the pressure at the available source is higher than needed at the engine or where the source pressure varies widely, I insert a reducing valve or other means between the source and the engine to reduce the pressure as needed and provide a reasonably nonvarying pressure for the engine. The introduction of this fuel to the engine cylinder should be positively timed, as by a valve controlled by the engine crank shaft or a cam shaft; a valve timing the injection period solely by differences of pressure on its two sides is likel to be too diflicult to adjust and maintain su ciently accurately timed. Also the fuel input should be completed rather early in the compression stroke, so as to afford'time for thorough mixing of the gas and air within the cylinder during the remainder of the compression stroke, as well as for other reasons; on the other hand the input periods ought not be so short as to require such high gas pressures as to entail difficulties in governing or otherwise, or in any other way render the introduction of the proper amount of gas fuel unduly difiicult or complicated. Preferably therefore I put the fuel inlet port remote from the exhaust port, so that the fuel input can be begun at an early stage, and to this end and also to maintain so far as possible the simplicity of construction which two-cycle operation permits, I put the fuel inlet port at the compression end of the cylinder, preferably in the cylinder head, and pierce the exhaust port in the cylinder wall at a point where it is uncovered by the piston near the end of the power stroke as in ordinary two-cycle engine practice. Also as to permit the use of rather low gas pressures), and still finished so early in the compressionstroke as to assure good mixing. Ordinarily I employ a gas pressure of about fifteen pounds per square inch above atmosphere, although this figure may be departed from; this pressure, with the ports arranged as described, permits gas inflow during about thefirst forty-five percent of the compression stroke. Finally, the engine is. controlled by enlarging and reducing the fuel charges as;changes 1n the load or speed or both de- I 'mand, preferably, for simplicity, without variation of the air charges. A governor may be used, or ,the control can be by hand or otherwise. By whatever means the control is effected however, whether by varying the action of the fuel inlet valve, by a special timing or period measuring valve, by a throttle,

or otherwise, the pressure of the fuel gas should be maintained relatively constant at the point of control during the fuel input periods (i. e. at the variable-action inlet valve,

the special control valve, the throttle or whatever the control element may be). For this purpose, I employ a feature somewhat resembling a feature heretofore used with ordinary two-cycle engines operating on-gas fuel derived from an available source of gas under pressure, namely, a capacity of such size or kind or both in the gas line as to maintain suitable constancy of pressure. This capacity may be in the form of a resers voirtank, an enlargement in the gas line, or a gas line oversize throughout. This capacity I insert between the point of control and the pressure reducing valve heretofore mentioned, quite as has been customary with twocycle gas engines of ordinary form, but with this difference: With the ordinary form of gas engines, since the fuel and air mixture pass into the engine against a pressure only slightly above atmospheric, the pressure maintained in the storage reservoir by the reducing valve is only slightly, a matter of ounces or a pound or two, above the atmospheric pressure; according to my invention,

the pressure maintained in this reservoir is considerably greater, such as the fifteen pounds above atmospheric heretofore mentioned. Furthermore, because of the higher pressure, the gasometer frequently used with the ordinary two-cycle engine is not adapted to serve as the capacity for my, invention. This capacity should be of sufficient size to render the control of the engine reliable, and preferably large enough to avoid violent action on the part of the reducing valve; also it should be so close to the control point (that is to say, without such intervening piping, restrictions to gas flow, etc.) that the requisite constancy of pressure is carried through to the control point. Where a number of engines or a number of cylinders operate from the same source of gas, this capacity may be in the form of a common fuel header for example, with a. single reducing valve or similar between it and the source.

In order that the range of control may be as large as possible, that-is to say, in order that the widest range of load and speed variations may be accommodated, the spark-plug or other igniter is located, preferably, as close as convenient to the fuel inlet port, or other provision is made for having adequate fuel for firing close to the igniter at the moment cycle der as well a single cylinder engines. Also it will be apparent that my invention is applicable to engines in which two pistons operate inopposite directions in the same cylinder; in such engines it will be understood that my reference herein to the cylinder head includes the clearance space between the two pistons.

The invention is illustrated diagrammatically in the accompanying drawing in connection with a single cylinder engine.

The engine cylinder (water jacketed) is illustrated at 1 and the piston at 2. The exhaust port is pierced in the side of the cylin der at 3, and the air inlet port at 4, both Where the piston 2 acts as a valve therefor as in accepted two-cycle practice. As is common also in two-cycle practice, the side of the piston toward the crank shaft is used to compress the air. For that purpose, in the present instance, the crank'side of the cylinder is closed by a Wall 7, a passage 8 connects the chamber between the wall 7 and the piston 2 with the air port 4 and a suction valve or valves 9 are provided. Each compression stroke of the piston 2 sucks the valve 9 open, and thus charges the chamber-between 2 and 7 with air; each power stroke of the piston compresses this air, and as the piston uncovers ports 3 and 4, this air passes through the passage 8 and air inlet port 4 to scavenge the cylinder and recharge it with combustion air. To accommodate the wall 7, the engine illustrated is provided with a cross head 10, the guides for which are indicated at 13; the piston rod 14 passes through a gland 15 in the wall 7, and a connecting rod 16 connects the cross head to the crank 17 of the engine crank shaft 18.- A spark plug 19 ignites the charge; the operation of the spark plug may be assumed to be controlled by the crank shaft 18 (or the cam shaft 20 later described) in substantial accordance with ,ordinary twoactice.

It will be observed from the foregoing that the fluid entering through the port 4 may be air alone taken direct from the atmosphere. Thegas fuel enters the cylinder through the fuel inletport 24 in the cylinder head, and hence close to the igniter 19, and remote from the exhaust port 3. a In the present instance, this fuel inlet port has a poppet form of valve 25 which is urged to its seat by a spring 26 surrounding the valve stem. A rock lever 27', push rod 28, cam lever 29 and cam 30 on the cam shaft 20, act at the proper time to open the fuel valve 25 and hold it open for the desired period. Gas then flows into the engine cylinder through the fuel line pipe 31. The cam shaft 20 is gearedto the crank shaft 18 through the gears 32 and 33, which can be assumed to have aone-to-one ratio, so that the cam shaft 20 is driven at the same angular speed as the crank shaft; hence gas enters the cylinder once during each revolution of the crank shaft. As before mentioned,

with the ports arranged" about as indicated in the drawing, I have found that the gas admission can be begun, that is to say the inlet valve 25 can be opened, before the exhaust port 3 is closed; the exhaust port 3 being remote from the inlet port 24, the inflowing gas fuel is unable to reach the exhaust port before the latter is covered again by the piston. Using a pressure in the fuel line of about fifteen pounds per square inch above atmosphere, I ordinarily close off the gas inflow at the end of about the first forty-five per cent of the compression stroke. Hence ordinarily I so locate the cam 30 that it opens valve 25 just about at the beginning of the compression stroke and make it long enough to hold this valve open until the compression stroke is about forty-five per cent completed. A governor at 35 is geared to the cam shaft 20, and acts through the valve at 36 (illus-' trated as an ordinary form of balanced throttle) to control the flow of gas through the pipe 31 to hold the engine speed constant; when the speed tends to rise above or fall below some value at which the governor is set,

the governor closes or opens the throttle valve g which gas is found and in which it is formed usually under a pressure at least equal to that required to force the gas fuel into the cylinder through the inlet port 24 against the (comparatively) low pressure (above atmosphere) within the engine cylinder during the beginning of thecompression stroke. It will be observed that it is not outside my invention that the source 37 be supplied with gas, in whole or in part, by a pump driven by the engine receiving its gas supply from this source the points is, that the source 37 is not solely for supplying the engine, but is inherently a source of gas for other purposes, the gas supplied to the particular engine being ordinarily but a small fraction of; the total amount of gas supplied'bythe source 37 for all purposes. Ordinarily in the" gas line 38, 39, 40, 41 and 31, I insert a pressure reducing valve 42 or other means for reducing the pressure to the pressure desired at the throttle, for example fifteen pounds per square inch above the pressure of the atmosphere, and/or for preventing thetransmi'ssion to the throttle and engine of any variations in the pressure that may occur in the source 37, as necessary. I herein refer to all such means as pressure reducing valve. At 40, namely between the pressure reducing valve 42 and the throttle '(point of control) 36 is the capacity hereinbefore discussed, and here shown in the form of an enlargement in the fuel line; 40 maybe solely for the engine illustrated or a header from which a number of engines similar. to that illustrated are supplied. Pipe 41 conducts the gas for the engine illustrated from the capacity 40 to the throttle 36.

It will be understood that my invention is not limited to the details of construction above described and illustrated in the drawing, except as appears hereinafter in the claims.

I claim 1. The combination of a two-cycle internal combustion engine of the kind indicated having means for admitting air for scavenging and for admitting fuel, the fuel being admitted during the compression stroke but so late as to avoid loss of fuel through the exhaust port, an available source of gas fuel under a pressure at, least equal to the pressure at which the gas is forced into the engine, a fuel line for leading gas from said source to the engine, control means for enlarging and reducing the charges of gas fuel, and a capacity related to the fuel line for maintaining a relatively constant pressure on the gas fuel at the control point.

' 2. The combination of a two-cycle internal combustion engine of the kind indicated having means for admitting air for scavenging and for admitting fuel, the fuel being admitted during the compression stroke but so late as to avoid loss of fuel through the axhaust port, an available source of gas fuel wherein the maximum. pressure is greater than the pressure at which the gas is forced into the engine, a fuel line for leading gas from Study source to the engine, a reducing valve in said 3. The combination of a two-cycle internal combustion engine of the kind indicated having means for putting in air for scavenging, a port for admitting gas fuel at the cylindervalve in said line, control means for enlarging and reducing the charges of gas fuel having its point of control between said reducing valve and the engine, and a ca acity related to the fuel line between the re ucing valve and said point of control.

4. The subject matter of claim 3, characterized by the fact that the fuel inlet port is so related to the engine igniter that fuel is had at the igniter at the moment of ignition.

5. The combination of a two-cycle internal combustion engine having means for admitting air for scavenging and for admitting fuel, fuel being admitted during a considerhead end of the cylinder, an exhaust port in the cylinder wall at a point where the port is uncovered by the piston near the end of the power strokes, and engine-operated valve means controlling the admission of gas throughsaid gas fuel port and timed to begin the fuel admission near the beginning of the compression stroke but, too late to permit substantial loss of fuel through the exhaust port, an available source of gas fuel under a maximum pressure exceeding that of the pressure at which the gas fuel is forced into the engine, a fuel line for leading gas from said source to the engine, a pressure-reducing CERTIFICATE or CORRECTION.

Patent No. 1,747,171. Granted February 18, 1930, to

ALFRED w. HUBBELL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 102, for the word "formed" read found, and line 113, for -"points" read point; and that the said Letters Patentshould be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 21st day of June, A. D. 1932.

J. Moore, 1

(Seal) Acting Commissioner of Patents.

CERTIFICATE OF CORRECTION.

Patent No. 1,747,171. Granted February 18, 1930, to

ALFRED W. HUBBELL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 3, line 102, for the word "formed" read found, and line 113, for "points" read point; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 2lst day of June, A. D. 1932.

M. J. Moore, (Seal) Acting Commissioner of Patents. 

